6061-T6 Aluminum Alloy Research Articles

Web crippling behaviour of high-strength aluminium alloy channel-shaped members with strengthened web holes: Numerical study and new design rules

This study presents a detailed numerical investigation of 7075-T6 and AA-6086 high-resistance aluminium alloy channel-shaped members with strengthened web holes in web crippling. A nonlinear finite element (FE) model was developed and validated against the test results reported by the authors and other researchers. The material properties of 7075-T6 and AA-6086 high-resistance aluminium alloy were also obtained from the literature. Utilising this validated model, an extensive parametric study including 1296 models was carried out. This study examined both cases with clamped and unclamped flanges, and the variables were web thickness, bearing lengths, diameter of web holes, stiffener lengths, internal corner radii, and grades of aluminium alloys. Given the absence of existing standards for calculating the web load-bearing resistance of such members with strengthened web holes, the numerical results obtained from the parametric study were used to develop new design formulas with new coefficients through regression analysis. The design strengths calculated by the proposed design formulas were then compared against the FE results. Finally, a reliability analysis was also performed, demonstrating that the proposed design formulas can accurately predict the web load-bearing resistance for these members.

Effect of Layer Thickness in Cold Metal Transfer Cladding of Fe-Based ER70S-6 Alloy on AA 6061-T6 Aluminum Alloy

Effect of Layer Thickness in Cold Metal Transfer Cladding of Fe-Based ER70S-6 Alloy on AA 6061-T6 Aluminum Alloy

Ultrasonic peening-waterjet composite surface modification of 7075-T6 aluminum alloy for residual stress release and transformation mechanism

The release and transformation mechanism of residual stress contributes to the improvement of metal materials' processing and performance, enhancing their structural stability, surface integrity, and fracture resistance. This paper focuses on the Ultrasonic Impact Treatment-Solid Particle Entrainment by Waterjet (UIT-SPEWJ) composite surface modification of 7075-T6 aluminum alloy, investigating the effects of UIT-SPEWJ process parameters (jet pressure and target distance) on the alloy's surface quality, roughness, microhardness, residual stress, and the evolution mechanism of microstructure. The results indicate that the 7075-T6 aluminum alloy modified by UIT-SPEWJ mainly exhibits a "meteorite crater" effect, accompanied by significant smearing and ploughing phenomena. Surface roughness shows a trend of first decreasing and then increasing with the rise of jet pressure and target distance. The minimum surface roughness, 0.852 μm, is achieved at a jet pressure of 25 MPa and a target distance of 7.5 mm. The microhardness of the samples modified by UIT-SPEWJ gradually decreases from the surface to the substrate with increasing depth. The hardened layer depths of the samples UIT-SPEWJ-1–6 after modification are approximately 174 μm, 226 μm, 200 μm, 196 μm, 176 μm, and 172 μm, respectively. After UIT, SPEWJ, and UIT-SPEWJ surface modifications, the surface of 7075-T6 aluminum alloy mainly exhibits compressive residual stress (CRS). The surface residual stress σ_srs of samples modified by UIT and SPEWJ are approximately 195.161 and 215.752 MPa, respectively. The surface residual stresses of UIT-SPEWJ-1–6 samples are significantly improved to 277.089, 529.499, 393.615, 459.261, 368.084, and 220.635 MPa, respectively, with UIT-SPEWJ-2 sample having the highest surface residual stress, which is 2.7 and 2.4 times that of UIT and SPEWJ modified surfaces. Samples modified by UIT-SPEWJ present significant dislocation phenomena, and the precipitated phases mainly include the needle-like metastable phase η', as well as the equilibrium phase η (MgZn2) with a rod-like structure. At lower jet pressures and larger target distances, the 7075-T6 aluminum alloy exhibits a continuous PFZ with a size of approximately 12–23 nm. As jet pressure increases and target distance decreases, discontinuous grain boundary precipitate bands appear, sized around 8–17 nm. Moreover, when the jet pressure is 25 MPa and the target distance is 7.5 mm, the grain boundary precipitated phases are more dispersed.

A probability density function of stress amplitude applicable to power spectral density curves of structural random vibration response

The power spectral density curves of the random vibration response of a plate specimen with different spectral width coefficients were obtained by selecting different frequency ranges, and the probability distributions of the stress amplitudes were obtained by applying Monte Carlo method and rainflow counting method. Each probability distribution was divided into three segments by the corresponding zero-order spectral moment value, and each segment was fitted using either a Rayleigh function or an exponential function. Finally, a probability density function of stress amplitude was proposed by combining two Rayleigh functions and an exponential function. The proposed probability density function can be used to obtain the stress amplitude probability distribution for the power spectral density curves of structural random vibration response with any bandwidth, and the accuracy of the proposed function was verified based on the response data of a specimen of 7075-T651 aluminum alloy material under the action of six typical power spectral curves.

Investigation of Two Laser Heat Treatment Strategies for Local Softening of a Sheet in Age-Hardening Aluminum Alloy by Means of Physical Simulation

AbstractCar manufacturers increasingly aid high-strength aluminum alloys for their advantageous weight-to-strength ratio, but their limited formability poses challenges in plastic deformation processes. Tailored heat-treated blanks (THTBs) are a propitious approach to improve formability. Surface laser treatment is the predominant technology for obtaining THTB. To design this process quickly and accurately, without material waste, the use of physical simulation is increasingly promising. It allows replicating the process on a lab-scale and studying posttreatment mechanical and metallurgical properties. By adopting Gleeble® physical simulator, this study investigates the softening effects of local surface laser heat treatment on a EN AW 6082 T6 aluminum alloy blank. Two laser movement strategies—single linear path and multiple rectangular paths—were investigated at two treatment speeds for each. A finite element (FE) model was developed for simulating the process under all explored conditions. FE-derived thermal cycles were reproduced by means of physical simulation. After physical tests, alloy mechanical properties were evaluated. Results show that these properties depend on both the peak temperature thermal cycle and the interaction time between the laser source and the material surface. The comparison between the two strategies revealed that the multiple rectangular paths strategy allows to achieve a wider softened area at comparable interaction times.

Temperature-gradient and isothermal creep tests on 2024 aluminum alloy: A novel approach to creep failure evaluation aided by image processing

In high-temperature working conditions, the temperature difference between parts is common, and it is necessary to perform a temperature gradient test to predict creep behavior of alloy in real working conditions. In this study, a novel temperature gradient creep (TGC) test aided by an image processing method (IPM) was designed and performed on 2024-T3 aluminum alloy. The tests were performed under the conditions of isothermal tensile creep (ITC) and TGC in the temperature range of 285–315 °C under two stresses of 90 MPa and 125 MPa. Several experimental investigations were conducted to evaluate the creep failure of the specimens. The results showed that the temperature gradient during the TGC test leads to changes in strain, strain rate, stress exponent, microstructure and damage amount in the samples. The creep strain and strain rate of the TGC are greater than those of the ITC at 300 °C and 285 °C, and the rupture life is shorter. Finally, the Larson–Miller parameter is calculated, and the mathematical relationships between the strain rates of the TGCs and ITCs in 90 MPa and 125 MPa, which can be used to predict the creep strain rate under isothermal conditions, are proposed.

Experimental Study of Laser-Induced Cavitation Bubbles near Wall: Plasma Shielding Observation

To investigate the plasma shielding of laser-induced cavitation bubbles near a wall, a pulsed laser with different energies was selected to induce cavitation bubbles on the surface of 7050-T7451 aluminum alloy. A high-speed camera captured the evolution of the cavitation bubble, while a fiber-optic hydrophone system collected the acoustic signals during the evolution. Finally, a confocal microscope was used to view and analyze the surface morphology of 7050 aluminum alloy. The experimental results indicate that as the laser energy increases, the diameter, the evolution time, the pressure of the bubble, and both the pit diameter and depth all increase. Beyond an energy level of 1.4 J, the maximum diameter and the evolution time of the laser-induced cavitation bubble begin to decrease; the maximum diameter decreases by 2.04%, and the first evolution time decreases by 3.26%. Plasma shielding was observed in this experiment. Considering that the essence of a laser-induced cavitation bubble is the interaction between a high-energy laser and a liquid medium, the abnormal decrease in the maximum diameter, evolution time, and sound pressure epitomizes the manifestation of plasma shielding.

Fatigue crack growth in AA6082-T6/AA7050-T6 bi-materials: Effect of plastic zone ahead of crack tip

The main objective here is the understanding of the effect of plastic zone ahead of crack tip on fatigue crack growth (FCG). For that, a numerical simulation of FCG was made, based on cumulative plastic strain, considering a bi-material composed by the 6082-T6 and 7050-T6 aluminium alloys. The first one has a lower yield stress but a higher critical cumulative plastic strain. The values of da/dN are higher for the 6082-T6 which means that the effect of the easier plastic deformation dominates over the effect of the higher critical cumulative plastic strain. The bi-material 6082-7050 showed a pronounced decrease of da/dN near the interface, which starts when the monotonic plastic zone ahead of crack tip reaches the material transition. This indicates that the crack tip deformation is affected by the material inside the monotonic plastic zone. On the other hand, the bi-material 7050-6082 shows an accentuated increase of da/dN, which starts when plastic deformation is observed ahead of transition. The elimination of the contact of crack flanks reduces drastically the transient effects, which indicates that these are linked with plasticity induced crack closure effects. Crack tip blunting was proposed to be the mechanism of plasticity induced crack closure explaining the trends observed.

Simulation of fatigue crack initiation life under compressive loading based on material meso-characteristics

The fatigue problem under compressive loading is common in the key components of aeroengine. Most of the fatigue life prediction methods studied in the past are macroscopic phenomenological methods based on a large amount of experimental data. Due to the difficulty in carrying out the fatigue test under compressive loading, the S-N curve or Manson-Coffin formula commonly used on the fatigue life prediction of material under compressive stress were obtained through fatigue tests under conditions where the average stress was greater than or equal to zero. Although the average stress can be corrected by some formulas, whether the life estimation formulas fitted by those fatigue test data are applicable to the fatigue life analysis with average stress less than zero has not been solved in engineering. And there were few studies on the influence of compressive stress on fatigue life at home and abroad. On the basis of Tanaka-Mura fatigue crack initiation theory, a mesoscopic model suitable for fatigue characteristic analysis under compressive loading was established in this article. The model verified the feasibility in predicting the fatigue initiation life using test data of 7075-T651 aluminum alloy under the compressive fatigue load.

Analysis of bullet impact test on aluminum alloy plates at varying thickness and velocities

Analysis of bullet impact test on aluminum alloy plates at varying thickness and velocities

Numerical simulation of welding residual stresses in 6082-T6 thin aluminum alloy

Thin plate aluminum alloys of the 6082 series are widely used in welded car bodies because of their excellent characteristics such as light weight and high strength. For welded joints, residual stresses significantly affect fatigue strength properties, especially in thin plate welding. In this study, the residual stresses arising from inert gas welding of thin sheet aluminum alloy metals were investigated using numerical simulation techniques. The thermo-elastic–plastic method was used to calculate simulated weld temperature and stress fields. Temperature and stress variations during the welding process were discussed to investigate the causes of residual stresses. The changes in stress during the experimental welding process were tracked, and the results were in agreement with the simulations. The impact of process parameters on welding stress was analyzed through simulation and experimentation. The results showed that residual stress decreases as speed increases and increases as power increases.

Corrosion failure analysis and solutions of aluminum alloy gas path plate used in sanding device of high-speed train

During the maintenance of a high-speed train, it was frequently found that the anodized aluminum alloy gas path plates in the sanding device had different degrees of corrosion. In this paper, SEM, EDS, XRD and LAD-EDTEST spectrometer were used to analyze the macro and micro morphology, elements and phases of corrosion product, element compositions of the matrix and assembly problem of the gas path plates. The mechanism of delamination spalling corrosion caused by local pitting corrosion of anodized aluminum alloy gas path plate was described. In addition, the properties of the coatings produced by different surface treatment methods and different substrate materials were compared. The test results indicate that the corrosion protection level of the micro-arc oxide coating is higher than that of the anodic oxide coating, which is mainly composed of γ-Al2O3 and contains a certain amount of α-Al2O3. Compared with 2A12-T4 aluminum alloy, the micro arc oxidation (MAO) coating of 6082-T6 aluminum alloy has lower porosity, higher hardness, higher corrosion potential, lower corrosion current, and better corrosion resistance, and 6082-T6 aluminum alloy is more suitable for use as the gas plate material. Meanwhile, it is proposed that the MAO coating with 35 μm can obviously improve the corrosion resistance of the gas path plate.

Experimental study and numerical simulation of cellular I-beam manufactured using refill friction stir spot welding technology

The paper presents analyses of thin-walled I-beams constructed from 6061-T6 aluminum alloy using refill friction stir spot welding (RFSSW). A parametrized finite element model of the reference cellular beam was developed, and the results from numerical simulations and experiments were compared. Subsequently, the validated numerical model was utilized to conduct an in-depth analysis of three additional beams featuring distinct cross-sections. To assess the weld behavior, experiments were conducted on samples composed of two sheets connected by two spot welds. The outcomes of these investigations underscore the suitability of RFSSW as a method for constructing thin-walled structures in civil engineering applications.

Experimental study on mechanical behaviour of friction stir welded aluminium alloy butt joints

The purpose of this paper is to understand the softening extent and stress-strain behavior of the normal-strength 6061-T6, 6013-T6, and high-strength 7075-T6 aluminium alloy butt joints using the novel friction stir welding (FSW) technique. A total of 107 monotonic tensile coupons and 33 Vickers hardness coupons were prepared from 8- or 12-mm thick welded plates using various tool rotation speed, welding transverse speed and tool configurations. The surface morphology, stress-strain curves and hardness distribution laws after welding were evaluated. The W-shaped hardness profiles were clearly observed, with the fracture location positively correlated at the lowest point of Vickers hardness near the edge of the weld toe. The strength reduction and softening extent of extruded aluminium alloys in T6 temper induced by FSW were superior to those of aluminium alloys using fusing welding process outlined in the Chinese and European standards, indicating the effectiveness and applicability of the FSW technique in the formation of components and connections for aluminium alloy structures. Additionally, the current widely used constitutive models generally yielded under-estimations on the strength under large strains. The developed three-stage Ramberg-Osgood model, using seven key input parameters, significantly improved the accuracy and consistent predictions in the full-range stress-strain curve of FSW aluminium alloys. Furthermore, the suggested model could still achieve a great balance between accuracy and practicality when using just three common available parameters with the employment of predictive expressions on other four parameters.

Investigating the formability of 6061-T6 aluminum alloy sheets at elevated temperatures using experimental and numerical methods

The high weight-to-strength ratio of AA6061 aluminum alloys presents increased potential applications in industries such as automotive and aircraft. However, its limited formability at room temperature (RT) restricts its usage. Therefore, in the conducted study, the formability of AA6061-T6 sheets with a thickness of 2 mm was investigated at different temperatures in the range of RT up to 300°C. Both experimental and numerical methods were employed to investigate the forming limit diagram (FLD) of an AA6061-T6 sheet. The tests were conducted using a non-isothermal Nakajima standard die under dry contact conditions. Two damage criteria, the Johnson–Cook and the ductile fracture criterion (DFC), were used in a thermomechanically coupled finite element analysis in Abaqus/Explicit to predict fracture in the AA6061 sheet. To examine the impact of temperature on the friction coefficient in the punch and sheet contact, an atomic force microscope was used to measure the roughness of the sheet, after the FLD tests, were conducted at different temperatures. Results indicate an increase in FLD levels from RT up to 100°C, followed by a decrease, for temperatures surpassing 100°C. Experimental findings underscored the significance of the adhesive wear at elevated temperatures, acting as a decisive factor that hampers the material flow and the sheet deformation, in the contact between the sheet and punch.

High-Temperature Oxidation of the 304/6061 Welding–Brazing Joint and Its Effects on Corrosion Characteristics

Laser–MIG hybrid welding–brazing was used to weld 304 stainless steel and 6061-T6 aluminum alloy with a thickness of 2 mm. The microstructure, morphology, chemical composition and corrosion behavior of the samples after high-temperature oxidation were investigated. The results reveal that the 304/6061 dissimilar joint had a thicker intermetallic compound layer (7–8 μm) during high-temperature oxidation (HTO) treatment than the sample without HTO treatment (2–3 μm). The oxide film thickness of the 6061 side of the weld joint treated by HTO (2401 nm) increased compared to the samples (181.1 nm) without HTO treatment. Unlike other metals treated by high-temperature oxidation, the high-temperature treatment process in this paper can reduce the corrosion resistance of the base metal and dissimilar joints, and the sequence of the corrosion current density was weld (HTO) >weld>6061 (HTO) >6061>304 (HTO) >304.

New ultra-low cycle fatigue model for metal alloys

Ultra-low cycle fatigue failure is an important ultimate limit state of the structures. Based on the ductile fracture model proposed by the authors, the Coffin-Manson model, and the Miner law, a new model was proposed in this study. The strategy of the proposed model is intended for the prediction of ultra-low cycle fatigue fracture onset covering a wide range of stress triaxiality and being suitable for the variable amplitude straining. Three kinds of metal alloys, Q345qC steel, G20Mn5QT cast steel, and 2024-T351 aluminum alloy, were used to verify the model. The results showed that the proposed model advanced the original Coffin-Manson model greatly. More importantly, the verification demonstrates that the proposed model can predict the ultra-low cycle fatigue fracture initiation over a wide range of stress triaxiality and under variable amplitude straining. Besides, compared with the ULCF-2021 model, the proposed model has a relatively lower average error.

Optimization of 2024-T3 Aluminum Alloy Friction Stir Welding Using Random Forest, XGBoost, and MLP Machine Learning Techniques.

This study optimized friction stir welding (FSW) parameters for 1.6 mm thick 2024T3 aluminum alloy sheets. A 3 × 3 factorial design was employed to explore tool rotation speeds (1100 to 1300 rpm) and welding speeds (140 to 180 mm/min). Static tensile tests revealed the joints' maximum strength at 87% relative to the base material. Hyperparameter optimization was conducted for machine learning (ML) models, including random forest and XGBoost, and multilayer perceptron artificial neural network (MLP-ANN) models, using grid search. Welding parameter optimization and extrapolation were then carried out, with final strength predictions analyzed using response surface methodology (RSM). The ML models achieved over 98% accuracy in parameter regression, demonstrating significant effectiveness in FSW process enhancement. Experimentally validated, optimized parameters resulted in an FSW joint efficiency of 93% relative to the base material. This outcome highlights the critical role of advanced analytical techniques in improving welding quality and efficiency.

Novel methods for optimizing CNC aluminum alloy machining parameters in polymer mold cavities

The examination of the machining of 7075-T6 aluminum alloy polymer mold cavities using Taguchi optimization and analysis of variance is presented in this paper. This study identified the best CNC milling cutting parameters and used a mathematical model to quantify the surface roughness of the machined cavities. The findings showed that while using a flat endmill, the spindle speed multiplied by feed rate contributed 28.01% to surface roughness, and when using a ball endmill, the squared depth of cut contributed 41.27%. Using both flat and ball endmills, the depth of the cut contributed 98.53% to the material removal rate. A refined second-order linear regression model was employed to forecast the endmill-machined surface roughness. The Warp Surf Portable tester measured values that were outside the error range of approximately 0.257% and 2.8%, respectively, for the expected values. Surface roughness has a 99.97% correlation coefficient in the regression model, indicating a very significant link. Additionally, the study improved the cutting parameters for a ball endmill, which were 3005 Rpm, 726.7 mm/min, and 0.43 mm, and for a flat endmill, these were spindle speed (2500 Rpm), feed rate (650 mm/min), and axial cut depth (0.5 mm). The outcomes demonstrated how well the techniques enhanced mold cavity machining and cost estimation using Ra and MRR data. Consequently, these results can be applied to future academic studies and industrial applications.

Initiation and growth of fatigue cracks in sheets with U-shaped notches in the first and mixed modes of fracture

Initiation and growth of fatigue cracks in sheets with U-shaped notches in the first and mixed modes of fracture